Electrical condenser



Dec. 11, 1928. 1,695,060

w. H. PRIESS ELECTRICAL CONDENSER Original Filed Oct. 22, 1919 3 Sheets-Sheet 1 INSULA'UON INSULATION 20 INVENTOR ll/L lliam/l Bias. /5

5 I5 7 A romvsy V Dec. 11, 1928. 1,695,060

/ -w. H. PRIESS ELECTRICAL CONDENSER Original Filed Oct. 22, 1919 3 Sheets-Sheet 3 INSULATION INSULATION \N5ULATION\ INSULATION JIINVENTOR Mllzam H F'ra'ass By W ATTORNE Patented Dec. 11, 1928.

UNITED STATES r "1,695,060. PATENT OFFICE.

WILLIAM H. PRIESS, OF BOSTON,'MASSACHUSETTS, ASSIGNOR TO WIRELESSSP ECIALTY APPARATUS COMPANY, OF BOSTON, MASSACHUSETTS, A CORPORATION OF NEW YORK.

ELECTRICAL CONDENSER.

Application filed October 22, 1919, Serial No. 332,421. Renewed September 26, 1925. i

If the dielectric such as mica and conductors are not in intimate contact, that is to say if a second dielectric in addition to the mica .is present between the conductors serious losses which may even extend to break down occur.

My invention is especially applicable to the type of stack in which the two ends are at difference of potential and is embodied preferably as an insulating clamp, that is, a clamp in which the two ends of the stack are connected by or insulated from each other by a member comprising insulating material. This material, must, however, be rigid and possess very little give and stretchability',

and for this purpose certain forms of vitreous insulating material such as porcelain, quartz glass and lavite have been found very serviceable. An advantage of my form of clamp resides in the fact that the capacity of the condenser remains constant with time and use.

My clamp may comprise means exerting a live pressure upon the opposite ends of the stack and maintaining the elements of the stack under constant pressure irrespective of variations in length thereof due to temperature changes, an increment of increase or decrease in the length of the stack being allowed by a corresponding change in the clamp due to its inherent resiliency or elasticity thus maintaining a constant pressure upon the ends of the stack. lVhen the stack expands the clamp yields enough to allow this and returns to its original position upon the contraction thereof. My clamp is therefore elastic, that is, when a strain is placed upon it and then removed the clamp returns to its original osition orstate.

An object 0? this invention is to provide a clamp which will maintain the insulators or dielectrics and conductors as above mentioned in intimate contact.

Another object of the invention is to provide a construction of clamp which will insulate the opposite ends of'the cuackifrom each other, maintain a substantially constant pressure on the ends of the stack irrespective of expansion or contraction'thereof due to temperature changes and hold the mica-or other Lnsplators and conductors in intimate con- This invention consists further in details of construction and combination of parts hereinafter more particularly described and claimed. 1

In the accompanying-drawings which form a part of this specification Fig.1 is an end elevation illustrating for the purpose of this application what I now consider to be the preferred form of the invention.

Fig. 2 is a side elevation, with parts in section, of the structure of Fig. '1 in a casing.

Fig. 3is a perspective view of a modified form of the invention, the casing (of Fig. 2) being omitted.

Fig. 4 is an end elevation of the type of condenser illustrated in Fig. 3.

Fig. 5 is-an end elevation of another form of the invention, the casing (of Fig. 2) being omitted.

Fig. 6 is an end elevation illustrating still another embodiment of the invention, the casing being omitted.

Fig. 7 is an end elevation of still another form of the invention, the casing (of Fig. 2) being omitted.

Fig. 8 is a plan view of a further form of the invention.

Referring to Figs. 1 and 2 the space X, Fig. 2, shown around the stack K and its clamp A in the wax or insulating'filler protector 'or casing B is intended to illustrate the wax casing or coating around the stack for the purpose of preventing brush discharges and excluding moisture and'air, and. also preferably but not necessarily around the clamp. This is preferably a mass of wax cast in protector B as a permanent. or temporary mold and filling the space X and surrounding stack K and permissively clamp A and it may be no more than a thin or surface coat providing that it excludes moisture and air from the interior of the stack and assists in preventing brush discharges.

In the type of condenser on which this in-. vention is an improvement, the condenser consists of a stack K of plates or sheets,'this stack being adapted for high potential service by being divided into sections which are electrically connected together in series by various means in accordance with the established practice for several years, and in which any desired manner of connecting these sections in series may be adopted, but for purposes of illustration I apply the arrangement as shown in Figs. 1 and 2.

The sheets as usual consist of successively located conductors and insulators. In the present condenser such insulating and conducting sheets may be of any desired material but I use metal foil (as lead) for the conducting sheets and mica for the insulating sheets and my condenser is therefore known to the trade as a mica condenser, or specifically a high potential mica condenser or as a transmitting condenser for use in radio communication. A desirable feature of a construction of this kindis the small volume of the entire apparatus, but the high potential developed across the ends of the sheet-stack makes this a diificult problem. The same is true in respect to exposing a minimum of the conducting parts which are at high potential. Other problems have arisen in connection with the importance of the construction whereby the condenser stack is most desirably held under compression and kept permanently dry and free from air inside of the stack and whereby brush discharges are prevented. W

I have illustrated clamp A Figs. 1 and 2, applied to a series of sections S constituting the stack K, the opposite ends of each section having foil bunches constituting terminals 1. Connectors 2 of sheet copper are interposed between the sections, one end, of each connector 2 being electrically connected to the foil bunch 1 at one end of one section and the opposite end of the connector being electrically connected to the foil bunch I at the opposite end of the adjacent section thus connecting the sections in series. Separators 3, usually mica are placed betweeneach connector and the adjacent section upon both sides of the connector for the purpose of insulating the adjacent portions of adjacent sections from each other and from the connectors.

The specific stack construction above described is more fully described, illustrated and claimed in the patent to Byron Macpherson, No. 1,446,650 of February 27, 1923, and is illustrated here merely to show an appli- .cation of the present invention, it being understood that the clamp embodying the present invention is applicable to other types of stack.

In assembling the apparatus, the stack K Figs. 1 and 2 is mounted upon or engages at one end an elastic base plate or'clamping member 4 composed preferably of tempered spring steel and before assembly assuming a bow or convex form'as illustrated in broken lines Fig. 1.

The opposite end of the stack is provided with a cast steel pressure member 5 covering the end and havin at opposite sides outwardly and upwardly projecting lugs 6.

Clamp A comprises blocks or plates 7 and 8 of rigid insulating material, preferably quartz, lavite or the like, vitreous material; and these insulating plates are provided at their upper portions with openings 9 (Fig. 1) made to correspond to the inclination of and to fit the inclined lugs 6 and in openings 9 are fitted or socketed the lugs 6 of the cast steel pressure member 5, thus supporting the insulating plates 7 and 8 at opposite sides of the stack over the surfaces of which these parts of clamp A extend, Fig. 2. The lower portions of the insulatin blocks or plates 7 versely extending metal inserts 10 thru which and thru the lower end of the block are screw holes 11.

Threaded-in these holes and thru the base plate 4 are adjusting screws 12 securing top pressure member 5 insulating blocks or plates 7, and 8 and the base plate 4.- All together in clamping relation around the stack K. In-the particular em bodiment of the invention here illustrated there are three' adjusting screws upon each side of the stack, and disposed at intervals, Fig. 2, across insulating sides 7. 8 of clamp A. Insulating plates 7, 8 of clamp A are of substantial width and height (Fig. 2), forming an insulating barrier and coperating with wax X between them and stack K in insulating the latter. The screws of each insulating block or plate 7 and 8 are or flexed drawing the same and t e pressure plate 5 toward each other clamping the elements of the stack in intimate contact at the required pressure. Securing the insulating blocks or plates 7 and 8 to the member 5 as illustrated insures that the former will be maintained locked and secured to the member 5 for the reason that as the screws 12 are adjusted to tighten the clamp the upper ends of the insulating plates 7 and 8 tend to move inwardly towardthe inner ends of the lugs 6 by reason of the inclination thereof.

The insulating plates 7 and 8 furthermore,

by reason of this connection are spaced from the sides of the stack and-the ends adjacent to the base plate t diverge from said sides. The wax X may fill this space between stack K and insulating-sides 78.

The adjusting screws 12 are located at the i and 8 are each provided with a series of transl opposite sides of the stack andupon ad justment apply pressure to the ends of the stack equally at opposite sides whereby the pres-' sure of clamp A is transmitted evenly or uniformly over the ends of the stack without danger of tilting or dislocating the. elements of the stack and compressing themv more on one portion than another. Vitreous insulating plates 7, 8 are the tension members of clamp A. Upon the adjustment of the screws 12 base plate 4 is flexed to assume the position or form shown in solid lines Figs. 1 and 2 transmitting a constant livepressure to the ends of the stack by reason of its tendency to assume a convex form.

The insulating tension blocks or plates 7, 8 are rigid or nonstretchable and capable of withstanding a heavy load so that the clamp by reason of its elastic member is highly elastic always maintaining a constant pressure and never works loose.

When the stack K is-placed in casing B and secured as hereinafter described, base plate 4 flexes or moves at opposite sides, upon variations in the length of the stack, around the pointsof connection, the ears 15-, of the plate 4 to the casing as an axis.

The clamping plate 4: may be of any strong metal such as tempered spring steel or may be of combination of metals sweated together such as steel and brass andso arranged as to automatically yield or flex as the temperature Varies maintaining a constant pressure great enough to keep the elements of the stack in intimate contact. v

In assembling the apparatus, the stack K is preheated and the screws 12 are tightened with the stack under pressure. All this will be done before placing the unit in the casing and securing it thereto thus allowing inspection of the stack before being surrounded by the wax or other insulating filler.

Of course, the stack K of this condenser like any condenser stack of sheets requires initial treatment during manufacture for the purposeof removing internal air and moisture and consolidating the stack of sheets before being covered with the coating of wax X which thereafter is to keep out the air and moisture. Any of the various well known methods may be used for this treatment, which usually includes immersion in molten wax, in or out of vacuum, and a compression or variation of the compression of the stack. For the latter purpose a clamp is used during the process but in this instance the clamp A, that is, the stack K and its clamp A may act as a unit during the treatment. The stack and clamp in the present case are assumedto have been'properly treated as above and in proper condition of clamping pressure and are ready to be inserted in casing B and surrounded by wax X or other filler.

The wax protector B is so called because it may serve initially as a mold for the wax casing X when the latter fills container B yet thereafter B may remain as a permanent part of the assembly for the purpose of protecting the wax filler which it does whether the filler be merely a coating around the stack or a thick mass filling protector B, or filling the space (Fig. 1) between stack K and the insulating plates 7, 8.

In preparation for the casting of the wax in receptacle B the stack K and the clamp A in place around it are inserted in protector B as a mold and protector. If desired indeed the receptacle B may be used previously for the above treatment of the stack i. e'., all three parts, stack K-, clamp A and receptacle B may be used together in the preliminary treatment of the stack.

The wax is then cast in the mold B around the stack and clamp. For this purpose the base plate 4 is provided with ears 15 having openings 16 adapted to fit around lugs 17 projecting upwardly from the bottom of casing B. Screws 18 are threaded into screw holes 19 in the central port-ion of lugs 17 se curing the plate 4. to the casing B. These points. of. attachment of the base plate 4 to the casing B are arranged at opposite sides ofthe former and upona line extending between and parallel to lines on which the adjusting screws 12 lie. As mentioned above this construction allows the portions of the base plate 4 to which the screws 12 are at tached to flex or move around these points of connection as an axis when the length of the stack varies.

Before the casing'B is filled with the wax X or other insulating filler one end of the lowest section S of stack K is connected by a lead 20 to the casing B. being soldered to the base plate 4 and preferably secured by one of the screws 18, as shown in Fig. 2 at the right.- The casing Bv if of metal may constitute the low potential terminal L P T, Fig. 2. Threaded to top compression member 5 of clamp A at right angles thereto is a brass terminal stud threaded at its upper end and constituting the high potential terminal H P T of the condenser. It will thus be seen that in the construction herein disclosed the end members 4 and 5 constitute in fact the terminals of the stack, altho not necessarily. lead 21 extends from one end of the uppermost section of the stack and is electrically connected to the cast steel pressure member 5 by being clamped thereunder. The casing B has a cover C of insulating material. This cover is provided with a vertically extending opening 22 to receive the stud H P T and with an uppervrecess 23 to receive a knurled metal insert 24 threaded to the upper portion of the stud. A look nut 25 is threaded upon the upper end of the terminalstud above insert 24 and above this is provided a nut 26 whereby any suitable electrical connection may be clamped.

The expressions high potential terminal and low potential terminal are, of course, only relative terms as the actual high potential and low potential depend entirely upon the condition of the circuit in which the condenser is used.

At the time when the stack and clamp are cast in wax X the high potential stud H P T is left projecting above the wax in preparation for the application of the condenser cover. After the wax in casing B has been cooled and solidified the top or cover C is applied on gasket G interposed for water tightness and around the terminal stud H P T. The insert 24 and the nuts 25 and 26 are then applied to the stud outside the cover and the cover is secured to the casing by the screws C.

The particular condenser here shown has a capacity of 0.004: micro-farad in extensive use for transmitters in radio communication. In the example disclosed each section S of stack K may consist of the size, number and thickness of sheets which will give it a capacity as above mentioned.

The wax protector or casing B may be of any desired material or shape because it has no necessary mechanical or electrical .cooperation wlth the condenser stack and the specific embodiment of clamp A herein disclose-d. Thus it may consist of any simple wood or fiber box of any size, or shape if desired. In fact as the stack K and clamp A (see Fig. l), constitute a complete operative condenser they may be used without any covering over the casting or coating of wax, but, of course, it is extremely advantageous to provide a wax protector and to also have it of metal as the most practical form of protector during use ofthe condenser.

I prefer that the casing B be of metal such as aluminum moulded thin to shape as a single and economic construction. Aluminum is light, relatively cheap and easily moulded but any other material may be used such as a tin or sheet brass casing.

The walls of container B are substantially vertical and the clamp A herein described is compact and allows the use of a casing B of relatively small size. The-insulatingplates 7 and 8 are of a substantial width, as great as orgreater than the width of the sides of the stack and of a length substantially as long as the stack whereby the adjacent portions of the sides of the stack are insulated,

in addition to the wax, if such wax be used,

(ill

from the adjacent walls of the casing preventing brushing.

In the construction herein disclosed the clamping means is entirely distinct from the insulating cover C and independent thereof,

the latter playing no part in'compressing' the stack, The cover therefore, if used, may

consist of any suitable insulating material of low structural strength such as 'electrose, or the like, molded to shape.

Referring to Figs. 3 and 4 I have 1llustrated a clamp embodying another form of the present invention.

The end sectionsS of stack K disclosed in Figs. 3 and 4 are provided with suitable leads 30 and 31 adapted to be connected to the high potential terminal and the low potential terminal as above described it a casing be used; otherwise they may be connected to any suitable terminals.

Upon one end of the-stack, Figs. 3 and 4, is placed a metal pressure plate 32 of an area corresponding to the area of the end of the stack. Interposed between the pressure plate 32 and the adjacent end of the. stack, which is built up of mica and foil as described above, is an insulating pad 33 to prevent injury to the end of the stack. At the opposite ends of they stack is an insulating sheet 34 for the same purpose.

My clamp A in the present'instance comprises plates or blocks 35 and 360i rigid insulating material such as above described, or even fairlystrong non-vitreous material such as the stronger forms of bakelite-dilecto, and of a length substantially the length of the stack and of a width substantially the width of the stack forming an insulating barrier and arranged upon opposite sides of the stack. The outside of each insulating block or plate is provided with apair of transverse grooves 37 arranged adjacent the ends thereof and inclined inwardly toward their adjacent ends. These grooves37 receive elastic orresilient claw shaped metallic clamping members 38 and 39 extending around the ends of the stack and having arms 40 extending toward one another along the sides of the stack and terminating in fingers 41 projecting into and engaging the grooves 37 in insulating plates 35, 36.

These claw shaped clamping members 38, 39'are of spring steel and constitute a pair of elastic clamping members forming a clamp of the double spring type as distinguished from the clamp disclosed in Figs. 1 and 2 in which only one of the end members is elastic. The results achieved however, are substan tially the same, that is, when the clamp including insulating tension members 35, 36 is adjusted to a given pressure maintaining the elements of the stack in intimate contact, the clamp maintains a constant live pressure upon theends of the stack irrespective of variations in length in the stack due to temperature changes.

In order to adjust initially the pressure exerted by this clamp uponthe ends of the stack one of the members 38 and 39, as here shown, member 38 engaging end pressure plate 32 is provided with adjusting means for drawing up the other member tightly against.

CJI

its end of the stack and for pressing plate 32 tightly against its end of the stack, compressing the elements of the stack. For this purpose this means comprises a plurality of set screws 42 extending. thru member 38 and having their inner ends engaging the pressure plate 32 as an abutment. These screws are symmetrically arranged whereby the pressure upon adjustment can be distributed uniformly over the ends of the stack to insure perfect contact of the elements thereof. It will be seen that as the screws 42 are adjusted the pressure plate 32 and the clamping member 39 will be moved toward each other clamping the ends of the stack. The clamping members 38 and 39 are elastic or resilient and become flexed by this adjustment maintaining a constant live pressure upon the ends of the stack whereby the. elements of the stack are maintained in intimate contact as above de scribed. Upon the adjustment of the screws 42 the pressure is transmitted to the opposite end of the stack thru the insulating plates or blocks 35 and 36 as tension members and the fingers 41 are drawn up in the grooves 37 with the parts, (members 38 and 39 and plates 35 and 36) tightly connected.

Referring to the modification of Fig. 5 stack K of series-connected sections S rests upon or engages at one end a spring plate or pressure member 51 of tempered spring steel, having a natural tendency to assume a convex form as illustrated in broken lines in the drawing, this construction being the same as or the equivalent of the plate 4 described in connection with Figs. 1 and 2. At the opposite end of the stack is a metal pressure memher 52 having a convex upper surface 52 and also having an area substantially as great as the end of the stack. The compression members 51 and 52 may constitute the electrical terminals of the stack which are generally at different potentials, it so desired. In this form a U shaped yoke 53 of rigid insulating material, preferably vitreous as above described, has an intermediate portion 54 extending ,over or engaging the convex surface 52" of the top pressure plate 52 and has ends 55 extending toward the base plate 51. diverging slightly from the sides of the stack. Adj usting screws 56 connect the .ends of the yoke 53 to the base plate 51. The screws pass thru the base plate 51. and are threaded into the ends of the yoke 53 and thru metal inserts 57 therein. These inserts insure that the screws receive a firm grip and distributes the stress uniformly over the insulating material. It will thus be seen that as the screws 56 are adjusted the end compression members 51 and 52 will be drawn toward each other putting insulation 53 under tension and clamping the stack sections S and the elements'thereof into intimate contact and the bottom curved pressure plate 51 will straighten out, exerting a live resilient pressure upon the ends of the o lating connectors 7 and 8 replaced by a single insulating yoke Fig. 6 illustrates another form of the invention in which the insulating tension members are employed and in which spring pres sure is applied to the ends of the stack by compressing a coil spring.

In this construction the stack K of series connected sections S rests upon or engages at one end a plate or pressure member 61 which covers the end of the stack and may be of any suitable rigid material preferably metal. The opposite end oi? the stack is provided with a metal pressure member 62 covering the end of the stack. The con'ipression members 61 and 62 may constitute the electrical terminals of the stack and for this purpose the member 62 is provided with a brass terminal stud 63 at right angles thereto and adapted to extend thru the cover of the casing, if such casing and cover be used as described 1n connection with Figs. 1 and 2.

The members 61 and 62 are maintainecl' clamped against the ends of the stack by the.

following means. Plates or blocks 64 of rigid insulating material, preferably vitreous as above described, are arranged at right angles to member 61 and secured thereto by screws 65 extending thru member 61 into the blocks 64: at opposite sides of the stack and thru metal inserts 66 therein for the purpose above described. The opposite ends of the blocks 64 are connected by a metal cross piece 67 by means of screws 68 at opposite sides of the stack and extending thru the cross piece into the adjacentends of blocks ,6Land thru metal inserts 69 therein for the purpose specified. The insulating plates or blocks 64 are arranged parallel with opposite sides of the stack in spaced relation thereto and project beyond the end on which the member 62' is placed whereby the metal cross piece 67 is spaced from said metal member 62. The

plates 6 act as insulating barriers insulating the sides of the stack as above described.

A coil spring 70 encircles the terminal stud 63 (which extends thru a hole 71 thru cross pieces 67), and is interposed between the member 62 and cross piece 67 which constitute abutments for the spring. Upon the adj ustment of either screws 65 or 68, or both, the bottom compression member 61 andtop cross piece 67 are moved toward each other, putting insulation 64 under tension and compressing the spring 0', increasing the. pressure on top pressure member 62, the spring pressure being transmitted to the opposite end of the stack and member 61 thru the tension plates 64 whereby the members 61 and 62 maintain a spring pressure on the ends of the stack. This spring is of suflicient strength to maintain the sections S and the elements thereof in intimate contact and to exert a constant live pressure upon the ends of the stack irrespective of variations in the length of the stack due to temperature spring as distinguished from the clamp here-- inbefore described in which an end compression member itself is springy.

In Fig. 7 I have illustrated a form of the invention in which the spring pressure is applied to the ends of the stack K having series sections S by a coil spring under tension as distinguished from the construction shown in Fig. 6 in which the coil spring is under compression.

The stack is provided at one end with'a pressure member 71 covering the end of the stack and at the opposite end with a pressure member 72 covering that end of the stack. These members may comprise any suitable rigid material preferably metal if used as terminals and need not be resilient.

Mounted outside of'or upon the member 72 parallel thereto is a member or cross piece 73 to which are attached (at right angles thereto upon opposite sides of the stack) plates'or blocks 74 of rigid insulating material, which extend along the sides of the stack toward the member 71, the member 7 2 being provided with suitable openings'75 to guide the blocks 74. The blocks 74 may be secured to the member 73 in any suitable manner as by threading or may be integral therewith if 73 be of insulating material. Coil springs 76 at opposite sides of the stack are connected at 77 to the free ends of the insulating blocks 74 and at their opposite ends to the pressure member 71, the insulating plates 74 terminating short of the member 71. The member 73 is provided with a plurality of set screws 79 extending therethru and engaging pressure member 72 which acts as an abutment for the set screws. These screws are symmetrically arranged so that the pressure can be adjusted uniformly on the ends of the stack maintaining perfect contact of the elements.

When the screws 79 are adjusted the springs 76 and insulation 74 are tensioned and the pressure members 71 and 72 are pressed or drawn against the ends of the stack. The springs 76 being under tension exert a live pressure upon the ends of the stack and hold the elements thereof in intimate contact under constant pressure irrespective of variations in thelength of the stack due to temperature changes.

In this construction also the end members .71 and 72 may constitute the electrical terminals of the stack, the opposite ends of which are preferably at highpotential differences and insulated from each other by the insulating plates 7 4;

In Fig. 8 I have illustrated a form showing another of the numerous ways in which the present invention is capable of embodiment. In this instance the stack K comprises sections S built up as above described and con nected in series in any suitable manner, although for purpose of illustration they are shown connectedin the same manner as in Figs. 1 and 2. At the opposite ends of the stack which are generally at a difference of potential may be located square plates 100 of rigid insulating material which are at least substantially the same area as the :toil sheets constituting the elements of the stack for the purpose of receiving the pressure of the clamp A transmitted to-the ends of the stack.

In this construction the clamp A comprised two elastic pressure end plates or -members 101 of tempered spring steel engaging the blocks 100 and connected together by plates 102 of rigid vitreous insulating material as above described and arranged upon opposite sides of the stack and forming an insulating barrier at the sides of the stack and spaced therefrom. The metal end plates 101 overlap the edges of the insulating blocks or plates 102 and are adjustably screwed or connected thereto by screws 103 passing thru the metal plates 101 and into the adjacent edges of the insulating plates -102 and thru the transversely extending metal inserts 104 placed in the metal plates 102 to insure a better grip for the-screws 103 and to distribute the stress uniformly ovcr'the insulation 102. In the form here illustrated there may be six screws passing thru each metal plate 101, three at each side of the stack whereby the pressure can be evenly and uniformly adjusted over the ends of the stack by way of insulation 102 under tension. v

The above construction provides an elastic durable clamp in which a live pressure is maintained upon the endsof the stack by elastic members at both ends, which are flexed and placed under tension when the clamp is adjusted to the required pressure by means of screws 103. The plates 101 tend naturally-to assume a convex formas shown in broken lines Fig. 8 (left) and when adjusted by screws "103 are straightened out which re sults in an inherent tendency for these plates to exert a live pressure against the ends of the stack, maintaining a constant live pressure Its lllu

' i. e., 4 and 10, the

on. the ends of the stack and the elements thereof in intimate contact irrespective of variations in length of the stack due to tem .perature changes. The above described stack and clamp constitute a complete condenser per se.

In the several forms of the invention described above, the insulating member or mem bers constituting part of the clamp are placed under tension when the clamp is adjusted to the required pressure.

The clamp and stack disclosed in Figs. 1 and 38 constitute a complete condenser, yet the unit maybe used with a separate casing and treated as hereinbefore described, it so desired.

The metal parts 10 of the stack'clamping means of Figs. 12 and 5-8, and the metal part 38 of Figs. 3-4, constitute an important feature of the invention in respect of the Vitreous tension-insulation and the'threaded clamp-securing and adjusting means. Taking Fig; 1 as typical, and irrespective of any clamp-flexibility as in bottom compression element 4, said member 4 and the adjusting screws 12 are of metal in accord with correct engineering design, the compression screws being located at a compressing angle when of vitreous material as an insulator having sufiicient strength to withstand the tension strains on the clamping means, is not adapted-structurally to withstand all strains when in direct combination with pressure screws 12. Hence, both ends of the screws are caused to enga e with metal members, l atter not only receiving the threads of screws 12, but being of a shape and relative arrangement which provide an ample bearing surface for engagement with insulating material 7-8, 1. e., as sufficient a bearing surface as that between the other compressionmember 5 and the other end of insulating barrier 7 -8, this hearing function of metal members 10 being in addition to their function in holding the threads of metal screws 12. Thus metal bearing members 10 and metal screws 12 may assume various shapes and locations relative to tension insulation 78 and the stack S, in respect of the function of bearing members 10 in receiving the screws 12 and in affording sufficient bearing surface with tension insulation 78. When metal screws 12 are screwed up, the metal bearing means 10, in which they engage, are forced in a direction away from the remote end of stack S, thereby tending to force insulation 7--8 in the same direction; theactual effect being that while all the parts, includin the remoteend of stack S, are held substantially rigid, save screws 12 and compression plate 4, et said screws and plate are moved toward the remote end of stack S, thereby putting it under compression. In

Figs. 34, the metal bearing means 10 of Fig. 1 and Figs. 5-8 is replaced by the metal hearing member 38, which bears against insulation 3536 in the specific way above described in respect to Figs. 3 1.

In brief, I have developed a clamp, of which several forms are illustrated and described, for keeping the series-sectional, highpotential condenser stack at all times under a constant pressure, said clamp comprising means for insulating the ends of the stack from one another, these ends having a high potential difference across them, and the in sulating portion of the clamping means constituting a tension element, altho consisting of vitreous material, such material being not only well, adapted for high potential insulation, but also having adequate structural strength to Withstand the high tension strains to which it is subjected in the construction and service of the condenser.

In all of the examples shown either the upper or the lower stack-compression member or both may be used as end terminals of the condenser unit.

It is to be understood that the invention is not limited to the embodiments and features specifically shown and described herein, but such embodiments and features are subject to change and modifications Without any departure from the spirit of the invention.

I claim 1. In an electrical condenser, a stack having its ends at a difference of potential and a clamp comprising pressure members upon the ends of the stack and rigid means consisting of structural insulating material and having portions extending along the sides of the stack and constituting the connection between said pressure members and transmitting the clamping stress longitudinally through said insulating means.

"2. An electrical condenser comprising a stack, pressure members engaging the ends of the stack and rigid insulating means adjust- .ably connecting said members and tensionedby adjustment.

3. In an electrical condenser, a stack having its ends at a,difierence of potential, and a clampcomprising pressure members engaging the opposite ends of the stack and rigid means consisting of structural insulating material and having portions extending along the sides of the stack and constituting the connection between said pressure members; and mechanism permitting tightening said pressure members against the stack ends thereby putting said insulating connection under tension. V

4. An electrical condenser comprising a stack, a pressure member at one cnd'of the stack and having upwardly and outwardly projecting lugs, a pressure plate at the opposite end of the stack; members of insulating material each having openings at one end and receiving said lugs thereby connecting said insulating members to said pressure member; and means for connecting the opposite ends of said insulating members to said pressure.

transversely of an end of the stack and in parallelism with the conductors and dielectrics for exerting spring pressure over the ends of the stack.

7. In an electrical condenser, a stack composed of sheets of conductors and dielectric and having its opposite ends at a difference of potential, and a spring clamp therefor com-.

, prising means insulating the opposite ends of said securing means to the. opposite end of of the stack from each other and means for adjusting said clamp for exerting a spring pressure on the stack. Y a

8. An electrical condenser comprising a stack and a clamp therefor including an elastic plate at one end of the stack, means for securing said plate at an intermediate portion thereof toa suitable support and means for connecting said plate upon opposite sides the stack.

9. In an electrical condenser, a stack of sections connected in series and comprising sheets of foil and dielectric, the opposite ends of said stack being at a difference of potential and clamping means exerting'uniform pressure over opposite ends of the stack, and ineluding means insulating the opposite ends of i the stack and held under stress whereby said .the stack from each other and a spring plate arranged to have its surface facing an end of pressure is maintained resiliently.

type, the combination with a stack of dielec trio and conductiing sheets arranged in serially-connected sections to have a high potential difference across its ends, a clamp for holding the stack under high compression, said clamp comprising a metal clamping member arranged adjacent to and to act against an end of the stack, metal means including a movable compressing member at the other end of the stack, and means consisting of rigid structural insulating material constitutingthe operating mechanical connection between said metal clamping member and metal means, said insulating means taking the tensile stress of the clamp and insulating the two metal end structures from one another.

11. An electrical condenser, comprising dielectric and conducting sheets arranged in serially-connected sections whereby the opposite ends of the stack in service have a difi'erence of potential, and clamping means arranged to exert uniform pressure over said stack ends, said clamping means including means insulating said stack ends from one another and including also a spring plate under stress whereby said pressure is maintained resiliently.

12. The combination with a series-sectional sheet condenser stack having a high potential difference across its ends, of two metal vwith the adjacentend of the rigid structural tension means; all whereby the screwing up of the metal threaded means causes the metal bearing means to put the rigid structural tension means under tension and force the two metal end compression means against the stack-ends.

13,. The combination with a series-sectional sheet condenser stack having a high potential difierence across its ends, of stack-clamping means comprising metal compression gneans res ectively located at the faces of the two eli s of the stack; said clamping means comprising also rigid vitreous tension means extending along the sides of the stack, having its ends mechanically connected with said two compression means and insulating them from one another; the mechanical connection be- I ftween said vitreous tension means and at- 10. In an electrical condenser of the sheet least one of said compression means including metal threaded pressure-applying means located at a compressing angle with said compression means, said mechanical connection including also bearing means of metal engaged by said metal threaded means and itself having a mechanical connection with the adjacent end of the vitreous tension means.

14. In an electrical condenser of the type including a stack having a high potential difference across its ends, the combination with such stack, of clamping means comprising two metal compression means respectively located at the end faces of the stack, said clamping means comprising also rigid vitreous tension means mechanically connected with said metal compression means, and extending along the sides of the stack and constituting an insulatin barrier for the stack from end to end thereo l5. Stack-clamping means for series-sectional sheet-stack condensers, which comprises two metal compression means respectivel having surfaces for en agement with the faces of the respective em? and tension means consisting of rigid vitreous insulating material mechanically connected with said two compression means.

16. Stack-clamping means for series-sectional sheet-stack condensers, which comprises metal end compression members connected together by tension means consisting of vitreous insulating material.

17. In a high potential condenser, the combination with a series-sectional condenser stack having a high potential difference across its end faces, of means for subjecting the stack to high vmechanical compression across its ends, said means including metal devices engaging the ends of the stack and therefore themselves at hi h potential dif;

ference, said means inclu ing also tension means constituting the operating mechanical connection between said metal end devices, said tension means consisting of structural insulating material withstanding the high tensile stresses and serving to insulate said metal'end devices of the clamping means from one another.

s of the stack,

18. An electrical condenser and a clamping system therefor comprising the following elements', namely the condenser comprising dielectric and conducting sheets arranged mechanically in a stack' and arranged electrically in serially connected sections thereby causing the two opposite end faces of the stack in service to possess a high potential difference; and the clamping system mechanically exerting a substantially constant live pressure upon the opposite ends of the stack while insulating them from one another by virtue of its construction comprising compression means extending over the surfaces of the end faces of the stack and compressing together the sheets of the stack, tension means extending along the sides of the stack and electrically insulated from the edges of the conduct-ing stack-sheets, means permittingadjustment of the cooperating compression and tension means to produce the desired compression on the stack ends; said clamping system including at least one elastic metal portion which it at the same potential as one end of the's'tack and which by its elasticity permits increases and subsequent decreases of the length of the stack while permitting the clamping system to maintain substantially constant stack-compression; and means electrically insulating said elastic metal portion from the other end of the stack at high potential difference.

WILLIAM H. PRIESS; 

